Sunday, April 1, 2012

WRF Showing Rotating Updraft Potential

This image shows the maximum updraft helicity. In other words, it shows the spinning of thunderstorms as they form, which could create a tornadic situation.
There is an abnormally high rate of helicity in Kentucky and Southern Indiana, which greatly worries me that the tornado risk may be a bit underestimated with instability around 1000 j/kg.


Supercells Possible in the Ohio Valley Today

There is a risk of severe weather today, as a currently ongoing cluster of storm cells moves southeast into the slight risk area.

Here is a skew-t valid for 21z today, a.k.a about 4 pm CDT. First, let's look at the instability (CAPE). When there is a large difference between the dashed line and the solid line, it means one of 2 things. If the dashed line is on the left, it means there is a lot of CINH, or storm-suppressing factors. If it is on the right, as it is shown here, there is a lot of CAPE, or storm-supporting factors.
There is a very large gap, indicating a large cape of about 2500-3000 j/kg, considered significant at this point in time.
I want to take a look at a few indices shown in the rows of parameters below the skew-t.

•Supercell Potential (3rd result, 2nd column) is at a very high 97 percent. Now, this means that, under very ideal conditions, supercells would be in a pretty good place to form. However, this does not mean that supercells will definitely form. I would still watch for that potential, however.

•ConvT, also known as Convective Temperature (1st row, 7th result) determines what temperature it would takes to get warm air to rise and form thunderstorms. To determine if the temperature will reach 80.1, the ConvT labeled here, I turn the lowest point of the solid line (temperature) from Celsius to Fahrenheit. The closer to the bottom of the image indicates closer to the surface. So, I take 29 Celsius and convert, giving me a temperature of 84.2 degrees. So, that means that warm air would be able to rise and form thunderstorms.

•STP (last row, 2nd result) is the Significant Tornado Parameter. Basically, it gives an idea of how likely tornadoes are. I personally don't trust it, as it can overestimate in some situations. The STP for this timeframe is 1.6, which is pretty low. But if there was an actual tornado predicting parameter, I would guess that the chance of a tornado would probably rest at 20-30%, which is pretty low. That doesn't mean I totally discount it, because who am I to make a tornado predictor?